# Featuring dark coronal structures: physical signatures of filaments and coronal holes for automated recognition

## TL;DR

This paper investigates how to distinguish solar filaments from coronal holes in EUV images using photometric, magnetic, and geometric properties, aiding automated solar feature recognition.

## Contribution

It introduces a multi-wavelength analysis combining EUV images and magnetograms to identify characteristic differences between filaments and coronal holes.

## Key findings

- Filaments and coronal holes have distinct photometric signatures.
- Magnetic properties differ between the two features.
- Projection effects influence the observed traits.

## Abstract

Filaments may be mistaken for coronal holes when observed in extreme ultraviolet (EUV) images; however, a closer and more careful look reveals that their photometric properties are different. The combination of EUV images with photospheric magnetograms shows some characteristic differences between filaments and coronal holes. We have performed analyses with 7 different SDO/AIA wavelengths (94, 131, 171, 211, 193, 304, 335~\AA) and SDO/HMI magnetograms obtained in September 2011 and March 2012 to study coronal holes and filaments from the photometric, magnetic, and also geometric point of view, since projection effects play an important role on the aforementioned traits.